1. Field of the Invention
The present invention concerns a pneumatic tire and a method of manufacturing the same, and more particularly, a pneumatic tire deploying an excellent puncture seal performance, without deteriorating the uniformity, riding comfort or the like of the tire and a method of manufacturing the same.
2. Detailed Description of the Prior Art
As a countermeasure for preventing a pneumatic tire from running over a nail or the like during the travel and being punctured, one provided with a seal material 30 of adhesive composition or the like, as puncture prevention layer 20, in an area corresponding to a tread 10 on the tire inner surface, as shown in FIG. 6 has been proposed. Even when this pneumatic tire treads, for instance, a nail into the tread 10 and the nail penetrates the tread, the puncture is prevented, because the nail hole is sealed with seal material 30 adhered around the nail.
However, as the seal material 30 is an adhesive liquid having fluidity, a phenomenon of flowing of the seal material 30 positioned in the tread shoulder area to the tread central area, due to the centrifugal force during a high speed revolution of the tire. Consequently, if a nail is stuck near the tread shoulder area, there was a drawback that it could not cope with the seal of this nail hole, reducing the puncture sealing.
As a countermeasure for resolving the flow problem due to the centrifugal force of such seal material, Japanese Patent Laid-Open 1978-45803 has proposed to form cells partitioned into a great number in an elastomer sheet, make an elastomer sheet where a seal material is divided and enclosed into these numerous cells, and paste this elastomer sheet to the tire inner surface. However, if a flat elastomer sheet is pasted all around the tire inner surface, there was a problem of deterioration in uniformity of the tire, because the splice portion where both end portions of the elastomer sheet are overlaid each other becomes heavier that the other portions, in the tire circumferential direction, and wrinkles or other form change are provoked in the curvature portion, in the shoulder area in the tire lateral direction.
Also, Japanese Patent Laid-Open 1978-55801 proposes to arrange a layer where seal material is dispersed in a soft rubber in a particulate form. However, as the particle of seal material is too minute in this tire, the sealing to the hole of the stuck nail is insufficient, and there was a drawback that it could not cope with a puncture due to a large nail or the like.
Besides, as a puncture prevention means without using a seal material, a run flat tire having a hard rubber or the like which is crescent in a cross section and inserted into the side wall as a reinforcement layer. However, this run flat tire has a drawback that the riding comfort lowers because the rigidity of the side wall increased due to the reinforcement layer.